1. Field of the Invention
The present invention relates generally to improvements in noncontact temperature pattern measuring devices and more prticularly pertains to new and improved temperature imaging systems utilizing active pyrometry techniques.
2. Description of the Prior Art
In the field of noncontact temperature pattern measuring devices, it has been the practice to employ passive pyrometry techniques to obtain the temperature image. Such devices have been unsatisfactory in that they provide true temperature images only if the local emissivity of the substance being measured is known. Failure to use the correct emissivity inevitably results in large measured temperature errors.
Examples of prior art imaging systems can be found in the U.S. Pat. Nos. issued to Tatsuwaki (4,365,307), Domarenok (4,403,251) and Tatsuwaki (4,413,344). All three of these patents are for imaging systems, but the pyrometry methods described for determining the temperature are that of two-color or multicolor passive pyrometry. A certain assumption must be made about the emissivity of the point of focus on the target: it is the same at the two (or more) different wavelengths. The Domarenok patent indicates the ability to compensate for varying emissivity across the target surface, but the constant emissivity with wavelength assumption still must be made for each point of focus. This assumption will be valid only for certain materials and temperature ranges, and as a result, can introduce large errors in the accuracy of the temperature measurement depending on the material used.
An example of active laser pyrometry used to measure the temperature of, a surface can be found in the Stein U.S. Pat. No. (4,417,822). The patent describes a system for noncontact measuring of the temperature of a body without knowing the emissivity. However, such measurement scheme is not shown as used in an imaging system.
The present invention provides a method for imaging a true temperature distribution on a given substance or target without physically having to touch the target and without knowing the localized emissivity of the target. According to the present invention, the foregoing and all the objects of the invention are attained by utilizing active pyrometry techniques in an imaging system.